SPERMATOGENESIS OF EUSCHISTUS 755 
THE ALLOSOMES 
A. The idiochromosomes and the discharge from the sperm nucleus 
These are those modified chromosomes called ‘chromatin 
nucleoli’ by me in 1898 and 1901, and ‘diplosomes’ in 1906 and 
1910. They correspond exactly to the bodies termed by Wilson 
‘jdiochromosomes,’ and I believe his term is preferable to either 
of mine in the present instance.® 
The behavior of these bodies was correctly described by me 
for the later growth period in 1898, their behavior during the 
maturation divisions first correctly elucidated by Wilson, and 
their main features have been later redescribed by me (06, 710). 
In the present paper are presented some facts on their behavior 
in the spermatocytes, and more especially their relations during 
the histogenesis of the sperm that has not been heretofore 
examined. 
In resting stages of the spermatogonia (figs. 1, 3,) they can- 
not be recognized, and there presumably compose a part of the 
nuclear reticulum; nuclear bodies that I had previously (’01) 
supposed to represent them in these cells I now believe to be the 
minute chromosomes (7m). 
The whole history of the spermatocytes, and particularly of the 
second maturation division, proves there is a pair of idiochromo- 
somes of unequal volume, and these, together with the twelve 
autosomes, compose the fourteen elements of the spermato- 
gonial mitoses (fig. 2); the smallest of the bodies is the smaller 
idiochromosome (d), but which is the larger cannot be told at 
this time, though it is probably one of the three next in size. 
Both idiochromosomes must divide in these mitoses, for all sperm- 
atocytes receive fourteen chromosomes, as we have seen while 
8 In ’06 the word ‘diplosome’ was applied by me to allosomes that occur in pairs 
in the paternal germ cells, diplosomes being a collective term for the two sets of 
structures that Wilson had distinguished as idiochromosomes and microchromo- 
somes; a monosome would be an unpaired allosome. I was well aware at that time 
that the name ‘diplosome’ had been previously employed for pairs of centrioles, 
but in that particular sense had fallen into abeyance in recent years. 
